Help with my microniche site!

So, I've decided to start with my Microniche website. I've found a good domain name, with good backlinks within my niche and i'm only waiting for godaddy to transfer it to my account. I've found several keywords within my niche, all are between 20-35 competition score. Now, what i plan on doing is creating an authoritative blog website with this somewhat microniche subject. However, i've found around 9 keywords within my niche that I could target. Some are a bit higher on the competition level and some are lower. Some have much higher search amounts than others as well. So, my question is should i be focusing on creating multiple blog entries for all 9 keywords at once or should i only be concentrating on one specific keyword. Furthermore, if i'm concentrating on all 9 keywords, i'm assuming i should be making blog posts specific to one keyword and not try to jam all 9 keywords in one posts correct? Any help or clarification on this would be super helpful, thanks!

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